Manufacturing of an integrated circuit (IC) has been largely driven by the need to increase the density of the integrated circuit formed in a semiconductor device. This is typically accomplished by implementing more aggressive design rules to allow larger density of IC device to be formed. Nonetheless, the increased density of the IC devices, such as transistors, has also increased the complexity of processing semiconductor devices with the decreased feature sizes.
Micro electro mechanical system (MEMS) is a technology generally referred to as miniaturized mechanical and electro-mechanical elements (i.e., devices and structures) that are made using the techniques of micro-fabrication. MEMS structures are recently developed in the field of integrated circuit technology in which MEMS devices are formed on a substrate to feature mechanical and electrical features. The MEMS devices include such as sensors, valves, gears, actuators, mirrors, heaters, printer nozzles and so on. Generally, a MEMS structure includes a substrate structure with MEMS devices and a cap structure, and the MEMS devices are positioned therebetween. In the manufacturing process of MEMS structure, further improvements are constantly necessary to satisfy the performance requirement in the scaling down process.